Abstract: A stand-alone toll-barring device powered by the telephone line voltage or from an external supply. The device recognizes a user's personal identification number (PIN) as it is dialed in from a telephone or similar peripheral device, and has device to recall rights (if any) corresponding to that PIN from a memory table, and a device to assess whether a number being dial just after entry of the PIN is permitted under those rights. Emergency numbers and incoming calls are not barred. If the number is not permitted, the call is immediately interrupted. Reprogramming of the data is provided by a further PIN. The device may be installed within a telephone or across fixed telecommunications wiring installations within a building. Should a larger range of permitted or denied numbers be required, multiple devices can be used in series.